MFH: r473352

Security upgrade mail/mailman to v2.1.27

Changelog:
https://bazaar.launchpad.net/~mailman-coders/mailman/2.1/view/head:/NEWS#L8

Release announcement:
https://www.mail-archive.com/mailman-users@python.org/msg70962.html

Reported by: portscout@ (release)
Security: 739948e3-78bf-11e8-b23c-080027ac955c
Security: CVE-2018-0618
Security: JVN#00846677
Security: JPCERT#97432283

Approved by: ports-secteam@ (miwi@)